I was curious about any "official" therapeutic horticulture in my community. I use the term "official" to differentiate between an organized program and that which is informal. I was discussing the topic with my sister-in-law, an avid gardener. When I described therapeutic horticulture she said, "Oh, we do that all the time!"
I didn't find any official theraperutic horticulture in my community, but there are places in Wisconsin. A very interesting site is at http://fyi.uwex.edu/therapeutichorticulture/
The first segment has a link to guide you to a discussion with the "Wisconsin Gardener" regarding the definition of therapeutic horticulture, but it leads you to a cooking segment. The link to the discussion can be found @ wpt.org/gardener/transcript/cfm?id=2126
However, the UW Extension site has several excellent examples of therapeutic horticulture including these stories:
1. Gardening is therapy for juvenile detainees
2. Therapeutic gardening helps residents with dementia
3. Local vets find solace in horticultural therapy
4. Green work: an innovative integrated employment training program for adults with cognitive disabilities.
It also has a list of Wisconsin programs which will prompt more investigation on my part.